Field of the Invention
Embodiments of the present invention relate to the technology field of a lighting device.
Description of the Related Arts
An LED (Light Emitted Diode) device is a device which converts an electrical signal to infrared rays or light using a property of compound semiconductor. Unlike a florescent lamp, since the LED device does not use harmful substances such as mercury and the like, it is less likely to cause environmental pollution and a long life span compared to a conventional light source. Also, it is advantageous that electricity consumed by the LED device is lower than electricity consumed by the conventional light source and the LED device has excellent visibility and low brilliantness due to a high color temperature.
Accordingly, a current lighting device has been developed from a structure, in which a traditional light source such as a conventional incandescent lamp or a florescent lamp is used, to a structure, in which the aforesaid LED device is used as a light source. In particular, by using a light guide plate as disclosed in Korean Laid-Open Patent Publication No. 10-2012-0009209, the lighting device which performs a surface light-emitting function has been provided.
The aforesaid lighting device has a structure in which a flat light guide plate is disposed on a substrate, and a plurality of side view type LEDs is disposed as an array on a side of the light guide plate. Here, the light guide plate is a type of plastic molding lens that functions to uniformly supply light emitted from the LEDs. Accordingly, in the conventional lighting device, the light guide plate is used as an essential component. However, due to a thickness of the light guide plate itself, there is a limitation to make the thickness of an entire product thin. Furthermore, as a material of the light guide plate is not flexible, it is disadvantageous that it would be difficult to apply the light guide plate to a part in which a bend is formed, and thus a product plan and design cannot be easily changed.
Also, as the light is partially emitted to the side of the light guide plate, light loss is generated. Thus, it is problematic that light efficiency is reduced. Furthermore, as a temperature of the LEDs increases at the time of light emission, it is also problematic that the LEDs' characteristics (e.g. luminous intensity and wavelength transition) are changed.